I'm developing an image matching system for a test set of 1000 images using SI_StillImage but keep hitting performance issues. As an example, when I first run the query below, it executes in around 60 seconds. The second run takes about twice as long and subsequent runs take progressively longer.

I've had similar issues with simpler matching, e.g. just using average color, which I've overcome by generating a table of results with pair wise image comparison scores in advance to use as a cache, but I can't do that in this case as ultimately, I'd like users to be able to specify the weights for each feature interactively.

I've a similar system in the past based on ORDImage signatures using the built-in indextype which worked really quickly in comparison but SI_StillImage doesn't have that option.